It's very useful when you need some simple transformation with data which you are going to display on a page or compare with something using EL.

But now I've already found and tested the best way to do it. This way is a creation of the custom EL function which performs your transformation. This solution is very elegant but it's now new. I found a lot of posts on the Internet dated 2006-... about this topic. But I just want to show you my solution and tell you what didn't work for me.